This invention relates to the field of microelectronic circuit fabrication. More particularly, this invention relates to routing signals with improved electrical performance and manufacturing yield.
As microelectronic devices get increasingly smaller, new problems with fabricating the devices emerge. For example, as the device sizes decrease, an increasingly greater number of contacts to the device need to be made within an increasingly smaller contact area. The number of contacts within a given surface area of an integrated circuit is generally referred to as the contact density. Obviously, as the contact density of the integrated circuit increases, so too will the contact density of the associated packaging for the integrated circuit tend to increase.
This situation of increasing contact density tends to create difficulties in providing the number of contacts required in a manner where the signal integrity through the contacts is maintained. Further, routing the signals through the contacts to the package presents additional challenges as the contact density increases. As the contacts become more tightly arranged, the cross-sectional area of the conductive materials through which the electrical signals are transmitted from the integrated circuit to the package is forced to become smaller. Since a conductor""s impedance becomes higher as the conductor""s cross-sectional area becomes smaller, the impedance of the conductive materials on the smallest integrated circuits can approach the upper design limits.
Also as integrated circuits become increasingly smaller, they become increasingly faster. When integrated circuits become faster, the electrical signals transmitted through the integrated circuit operate at a higher frequency. Higher frequency signals tend to increase the amount of cross talk between the signals and negatively affect the integrated circuits"" electrical performance.
Finally, as more of the conductive materials within an integrated circuit are fabricated near the upper design limits for the cross-sectional area, discontinuities in the conductive materials tend to become more frequent. Increasingly frequent discontinuities tend to reduce manufacturing yields and increase costs.
What is needed, therefore, is an improved routing configuration for the conductors within an integrated circuit.
The above and other needs are met by a structure for receiving electrical signals near a central portion of the structure and distributing the electrical signals to a peripheral portion of the structure. The structure has a first set of contacts arranged in an array near the central portion of the structure. Electrically conductive traces connect the first set of contacts to a second set of contacts, where each of the electrically conductive traces has at least a first segment, a second segment, and a third segment.
The first segment of each of the electrically conductive traces has relatively narrow width and spacing. The first segment of each of the electrically conductive traces is connected on a first end of the first segment to one of the first set of contacts and on a second end of the first segment to the second segment of each of the electrically conductive traces.
The second segment of each of the electrically conductive traces has relatively intermediate width and spacing. The second segment of each of the electrically conductive traces is connected on a first end of the second segment to the second end of the first segment and on a second end of the second segment to the third segment of each of the electrically conductive traces.
The third segment of each of the electrically conductive traces has relatively wide width and spacing. The third segment of each of the electrically conductive traces is connected on a first end of the third segment to the second end of the second segment and on a second end of the third segment to one of the second set of contacts.
Thus, by gradually increasing the width and thereby the cross-sectional area of the conductive material from a relatively small width near the central portion of the structure to a relatively large width near the peripheral portion of the structure, one is able to more easily route the tight geometries and the impedance of the conductive material is reduced. Additionally, the increased width provides conductive materials that are more resistant to discontinuities and breaks. As a result, fabrication tends to produce fewer defects, thus increasing manufacturing yields.
In one preferred embodiment of the structure, the structure is a circuit board. In this embodiment, the central portion of the circuit board receives a packaged integrated circuit. The electrical signals are then transferred between the circuit board and the packaged integrated circuit.
In another preferred embodiment of the structure, the structure is an integrated circuit package. The central portion of the integrated circuit package, in this embodiment, receives an integrated circuit. The electrical signals are then transferred between the integrated circuit package and the integrated circuit.
The electrically conductive traces may have more than three segments. Regardless of whether the electrically conductive traces have three or more segments, the segments generally gradually increase in width and spacing from the central portion of the structure to the peripheral portion of the structure.